A US environmental group has singled out apples as the worst offender among produce sold in the US when it comes to the amount of pesticides it carries.

In their seventh edition of the Shopper's Guide to Pesticides in Produce, the Washington DC-based Environmental Working Group ranked 53 fruits and vegetables -- sold in the US and grown either domestically or abroad -- according to their pesticide load, highlighting the most pesticide-laden foods in a list dubbed "The Dirty Dozen" and those that are lowest the "Clean15."